DEVELOPMENTAL PATTERNS DURING DIRECT SOMATIC EMBRYOGENESIS IN PROTOPLAST CULTURES OF EUROPEAN LARCH (LARIX-DECIDUA MILL)

Protoplasts isolated from embryogenic sus-pension cultures of European larch (Larix decidua Mill.) were cultured in thin alginate layers usi ng a nylon mesh to enable a monitoring of the development of single ce lls. The patterns of cell division and differentiation are characteriz ed and compared with zygotic embryogenesis to which homologies can onl y be drawn to some extent when the protoplasts grow in an auxin-free e nvironment. Already at 2.5 mu M both 2,4-dichlorophenoxyacetic acid or indole-3-acetic acid cause vacuolation and elongation of individual c ells, thus disturbing the process of somatic embryogenesis which gener ally lacks the precise quantitative patterns occurring in vivo. Prior to the formation of an embryo, a proembryonal mass develops. Oligonucl eated products of spontaneous protoplast fusions are able to cellulari ze even without preceding karyokinesis and perform a normal embryogeni c program.